Anchors for microelectromechanical systems having an SOI substrate, and method of fabricating same

ABSTRACT

There are many inventions described and illustrated herein. In one aspect, the present invention is directed to a MEMS device, and technique of fabricating or manufacturing a MEMS device having mechanical structures and anchors to secure the mechanical structures to the substrate. The anchors of the present invention are comprised of a material that is relatively unaffected by the release processes of the mechanical structures. In this regard, the etch release process are selective or preferential to the material(s) securing the mechanical structures in relation to the material comprising the anchors. Moreover, the anchors of the present invention are secured to the substrate in such a manner that removal of the insulation layer has little to no affect on the anchoring of the mechanical structures to the substrate.

RELATED APPLICATION

This application is a divisional application of application Ser. No.10/627,237, filed Jul. 25, 2003, now U.S. Pat. No. 6,952,041 thecontents of which are incorporated herein by reference.

This invention relates to electromechanical systems and techniques forfabricating microelectromechanical and nanoelectromechanical systems;and more particularly, in one aspect, to fabricating or manufacturingfor anchoring micromechanical and nanoelectromechanical devices tosemiconductor on insulator (“SOI”) substrates or the like.

Microelectromechanical systems (“MEMS”), for example, gyroscopes,resonators and accelerometers, utilize micromachining techniques (i.e.,lithographic and other precision fabrication techniques) to reducemechanical components to a scale that is generally comparable tomicroelectronics.

MEMS typically include a mechanical structure fabricated from or on, forexample, a silicon substrate using micromachining techniques. Thesilicon substrate is disposed on an insulation layer that, among otherthings, serves as a sacrificial layer for the MEMS. As such, significantportions of the insulation layer are etched or removed in order torelease the mechanical structure. (See, for example, U.S. Pat. Nos.6,450,029 and 6,240,782). In this way, the mechanical structure mayfunction, for example, as a resonator, accelerometer, gyroscope or othertransducer (for example, pressure sensor, strain sensor, tactile sensor,magnetic sensor and/or temperature sensor).

Conventional MEMS also employ the insulation layer to anchor themechanical structure to the substrate disposed below the insulationlayer. (See, for example, U.S. Pat. No. 6,240,782 and U.S. PatentApplication Publications 2002/0177252 and 2002/0118850). As such, whenfabricating such MEMS, the removal of the insulation layer is tightlycontrolled to avoid over-etching the insulation layer and therebyadversely impacting that portion of the insulation layer which anchorsthe mechanical structure to the substrate. In addition, such MEMS tendto include anchors having larger than necessary features to secure themechanical structures which are fabricated with large tolerances toensure sufficient anchoring of the mechanical structure under“foreseeable” variations in processing conditions.

Another technique for anchoring mechanical structure to the substrateemploys creating or etching a deep trench in the exposed silicon (i.e.,the silicon in which the mechanical structure is fabricated on or in)and the insulation layer underlying that silicon. The deep trenchcontacts the silicon layer that underlies the insulation layer of thewafer. Thereafter, the trench is filled with a low stress siliconnitride that is relatively unaffected during the release of themechanical structures. (See, for example, U.S. Pat. No. 6,569,754).

Anchoring techniques that employ deep trenches tend to be time consumingand expensive to manufacture as a result of creating the trenches in thethick silicon layer and underlying insulation layer. In addition, suchtechniques often experience difficulty in adequately filling the deeptrenches with a low stress material and, as such, tend to experience thedebilitating affects caused by pinholes, for example, cracking andcontamination.

There is a need for, among other things, MEMS (for example, gyroscopes,resonators, temperature sensors and/or accelerometers) that overcomeone, some or all of the shortcomings of the conventional anchors andanchoring techniques. In this regard, there is a need for an improvedtechnique to adequately anchor the mechanical structure in a costefficient manner that avoids the need for large tolerances and verytightly controlled etching and re-fill or deposition techniquesexperienced when using the conventional techniques.

SUMMARY OF THE INVENTION

There are many inventions described and illustrated herein. In a firstprincipal aspect, the present invention is a method of manufacturing anelectromechanical device having a mechanical structure including a fixedelectrode. The electromechanical device includes a substrate, aninsulation layer disposed on the substrate, and a first semiconductorlayer disposed on the insulation layer. The method comprises removingfirst portions of the first semiconductor and insulation layer tothereby a portion of the substrate and form an anchor opening. An anchormaterial (for example, silicon, silicon nitride, silicon carbide,germanium, silicon/germanium or gallium arsenide) may be deposited inthe opening to form the anchor. In this aspect of the invention, themethod includes depositing a second semiconductor layer over the anchormaterial and forming the fixed electrode from at least the secondsemiconductor layer that is disposed over the anchor material whereinthe fixed electrode is affixed to the substrate via the anchor material.

The method may also include forming a moveable electrode, juxtaposed thefixed electrode including defining the moveable electrode by removingfirst and second portions of the second semiconductor layer andreleasing the moveable electrode by removing the insulation layerunderlying the moveable electrode wherein the anchor material is notsubstantially removed when releasing moveable electrode.

In one embodiment, the insulation layer includes silicon oxide and theanchor material includes silicon, silicon nitride, silicon carbide,germanium, silicon/germanium or gallium arsenide. In another embodimentthe insulation layer is comprised of silicon nitride and the anchormaterial includes silicon, silicon oxide, silicon carbide, germanium,silicon/germanium, or gallium arsenide.

In one embodiment, a substantial portion of the fixed electrodeoverlying the anchor material is a monocrystalline silicon. In anotherembodiment, a substantial portion of the fixed electrode overlying theanchor material is a polycrystalline silicon.

In another aspect, the present invention is a method of manufacturing anelectromechanical device having a mechanical structure including fixedand moveable electrodes that reside in a chamber. The electromechanicaldevice includes a substrate, an insulation layer disposed on thesubstrate, and a first semiconductor layer disposed on the insulationlayer. The fixed electrode is affixed to the substrate via an anchormaterial. The method includes removing portions of the firstsemiconductor and insulation layer to expose a portion of the substrateand thereby form an anchor opening. An anchor material is deposited inthe anchor opening and a second semiconductor layer over the anchormaterial and the first semiconductor layer. The method further includesetching the first and second semiconductor layer to form the fixed andmoveable electrodes from the first and second semiconductor layerswherein the fixed electrode includes at least a portion of the secondsemiconductor layer that is disposed over the anchor material. Theanchor material secures the fixed electrode to the substrate.

In addition, the method of this aspect of the invention includesdepositing a sacrificial layer over the fixed and moveable electrodesand depositing a first encapsulation layer (for example, polycrystallinesilicon, amorphous silicon, silicon carbide, silicon/germanium,germanium, or gallium arsenide) over the sacrificial layer. Vents areformed in the first encapsulation layer to permit release of themoveable electrode by removing the insulation layer underlying themoveable electrode wherein the anchor material is not substantiallyremoved when releasing moveable electrode. Thereafter a secondencapsulation layer (for example, polycrystalline silicon, porouspolycrystalline silicon, amorphous silicon, silicon carbide,silicon/germanium, germanium or gallium arsenide) may be deposited overor in the vent to seal the vents wherein the second encapsulation layeris a semiconductor material.

In one embodiment, the insulation layer is comprised of silicon oxideand the anchor material includes silicon nitride, silicon carbide,germanium, silicon/germanium or gallium arsenide. In another embodiment,the insulation and sacrificial layers are comprised of silicon oxide andthe anchor material includes silicon, silicon carbide, germanium,silicon/germanium or gallium arsenide. In yet another embodiment, theinsulation layer is comprised of silicon nitride and the anchor materialincludes silicon, silicon oxide, silicon carbide, germanium,silicon/germanium or gallium arsenide.

In yet another aspect, the present invention is a method ofmanufacturing an electromechanical device having a mechanical structureincluding a contact and fixed and moveable electrodes. The electrodesreside in a chamber of the device. The electromechanical device includesa substrate, an insulation layer disposed on the substrate, and a firstsemiconductor layer disposed on the insulation layer. The fixedelectrode is affixed to the substrate via an anchor material.

The method of this aspect of the invention includes removing portions ofthe first semiconductor and insulation layer to expose a portion of thesubstrate and thereby form an anchor opening. An anchor material isdeposited in the anchor opening and a second semiconductor layer overthe anchor material and the first semiconductor layer. The methodfurther includes etching the first and second semiconductor layer toform the fixed and moveable electrodes from the first and secondsemiconductor layers wherein the fixed electrode includes at least aportion of the second semiconductor layer that is disposed over theanchor material. The anchor material secures the fixed electrode to thesubstrate.

The method also includes depositing a sacrificial layer over the fixedand moveable electrodes and depositing a first encapsulation layer (forexample, polycrystalline silicon, amorphous silicon, silicon carbide,silicon/germanium, germanium, or gallium arsenide) over the sacrificiallayer. Vents are formed in the first encapsulation layer to permitrelease of the moveable electrode by removing the insulation layerunderlying the moveable electrode wherein the anchor material is notsubstantially removed when releasing moveable electrode. Thereafter asecond encapsulation layer (for example, polycrystalline silicon, porouspolycrystalline silicon, amorphous silicon, silicon carbide,silicon/germanium, germanium or gallium arsenide) may be deposited overor in the vent to seal the vents wherein the second encapsulation layeris a semiconductor material.

In addition, the method includes forming a trench around at least aportion of the contact (wherein the contact and the trench as disposedoutside the chamber) and depositing a first material (for example,silicon oxide and/or silicon nitride) in the trench to electricallyisolate the contact. In one embodiment, the trench surrounds thecontact.

The method may also include depositing an insulating layer on at least aportion of the trench and, thereafter, depositing a highly conductivematerial on the contact and over the insulating layer to provideelectrical connection to the contact.

The insulation layer may be comprised of silicon oxide and the anchormaterial includes silicon nitride, silicon carbide, germanium,silicon/germanium or gallium arsenide. In another embodiment, theinsulation and sacrificial layers are comprised of silicon oxide and theanchor material includes silicon, silicon carbide, germanium,silicon/germanium or gallium arsenide. The insulation layer may becomprised of silicon nitride and the anchor material includes silicon,silicon oxide, silicon carbide, germanium, silicon/germanium or galliumarsenide.

In one embodiment, a substantial portion of the fixed electrodeoverlying the anchor material is a monocrystalline silicon. In anotherembodiment, a substantial portion of the fixed electrode overlying theanchor material is a polycrystalline silicon.

In another aspect, the present invention is an electromechanical devicecomprising a substrate, an insulation layer disposed on the substrate,and a first semiconductor layer disposed on the insulation layer. Thedevice may further include an anchor that is disposed in an opening inthe insulation layer and the first semiconductor layer and contacts thesubstrate. The anchor includes a material (for example, silicon nitride,silicon carbide, germanium, silicon/germanium or gallium arsenide) thatis different than the insulation layer. A second semiconductor layer maybe disposed on the anchor wherein a fixed electrode, formed in part fromthe second semiconductor layer, is affixed to the substrate via theanchor.

The device of this aspect of the invention may also include a moveableelectrode, juxtaposed the fixed electrode. The moveable electrode mayalso be formed, at least in part, from the second semiconductor layer.

In one embodiment, a substantial portion of the fixed electrodeoverlying the anchor material is monocrystalline silicon. In anotherembodiment, a substantial portion of the fixed electrode overlying theanchor material is polycrystalline silicon.

The device may also include a chamber including a first encapsulationlayer (for example, monocrystalline silicon, polycrystalline silicon,porous polycrystalline silicon, amorphous silicon, germanium,silicon/germanium, gallium arsenide, silicon nitride or silicon carbide)having at least one vent. The moveable electrode may be disposed in thechamber. A second encapsulation layer comprised of a semiconductormaterial (for example, monocrystalline silicon, polycrystalline silicon,porous polycrystalline silicon, amorphous silicon, silicon carbide,silicon/germanium, germanium or gallium arsenide) may be deposited overor in the vent, to thereby seal the chamber.

In one embodiment, the first encapsulation layer is a semiconductormaterial that is doped with a first impurity to provide a first regionof a first conductivity type. Moreover, the semiconductor material ofthe second encapsulation layer is doped with a second impurity toprovide a second region with a second conductivity type and wherein thefirst conductivity type is opposite the second conductivity type.

In another aspect, the present invention is an electromechanical devicesimilar to the previous aspect of the invention but also including acontact and a trench, disposed around at least a portion of the contact,including a first material disposed therein to electrically isolate thecontact. The contact and the trench, of this aspect of the invention,are disposed outside the chamber. In one embodiment, the trench isdisposed on an etch stop region. The etch stop region may be a siliconoxide or silicon nitride.

Notably, the trench may also include a second material surrounded by thefirst material and wherein the second material is a semiconductormaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the detailed description to follow, reference will bemade to the attached drawings. These drawings show different aspects ofthe present invention and, where appropriate, reference numeralsillustrating like structures, components, materials and/or elements indifferent figures are labeled similarly. It is understood that variouscombinations of the structures, components, materials and/or elements,other than those specifically shown, are contemplated and are within thescope of the present invention.

FIG. 1 is a block diagram of microelectromechanical system disposed on asubstrate, in conjunction with interface circuitry and data processingelectronics;

FIG. 2 illustrates a top view of a portion of micromechanical structure,for example, a portion of an interdigitated or comb-like fingerelectrode array, having “moveable” electrodes and “fixed” electrodes, ofan accelerometer, in conjunction with a contact area;

FIG. 3 illustrates a cross-sectional view (sectioned along dotted linea-a of FIG. 2) of the portion of the interdigitated or comb-like fingerelectrode array and contact area of FIG. 2, in accordance with certainaspects of the present invention;

FIGS. 4A-4F illustrate cross-sectional views of the fabrication of themicrostructure of FIG. 3 at various stages of the process, according tocertain aspects of the present invention;

FIG. 5 illustrates, among other things, a cross-sectional view of themicrostructure of FIG. 3 that employed non-conformal deposition, growthand/or formation techniques of single vs. polycrystalline crystalstructures;

FIG. 6 illustrates a cross-sectional view (sectioned along dotted linea-a of FIG. 2) of the portion of the interdigitated or comb-like fingerelectrode array and contact area of FIG. 2, in accordance with certainaspects of the present invention;

FIGS. 7A-7G illustrate cross-sectional views of the fabrication of themicrostructure of FIG. 6 at various stages of the process, according tocertain aspects of the present invention;

FIG. 8 illustrates a cross-sectional view (sectioned along dotted linea-a of FIG. 2) of the portion of the interdigitated or comb-like fingerelectrode array and contact area of FIG. 2, in accordance with certainaspects of the present invention;

FIGS. 9A-9D illustrate cross-sectional views of the fabrication of themicrostructure of FIG. 8 at various stages of the process, according tocertain aspects of the present invention;

FIGS. 10A-10D illustrate cross-sectional and top views of an isolationtrench according to certain aspects of the present invention;

FIGS. 11A-11F illustrate cross-sectional views of the fabrication of amicrostructure, having a trench isolated contact, at various stages ofthe process, according to certain aspects of the present invention;

FIGS. 12A-12E, 13A and 13B illustrate cross-sectional views of MEMSaccording to certain aspects of the present inventions, including amicromachined mechanical structure portion and an integrated circuitportion, both portions of which are disposed or integrated on or in acommon substrate; and

FIGS. 14A and 14B illustrate cross-sectional views of the fabrication ofa micromechanical structure, having a plurality of microstructures and acontact, which are monolithically integrated on or within the substrateof a MEMS, in accordance with certain aspect of the present invention.

DETAILED DESCRIPTION

There are many inventions described and illustrated herein. In oneaspect, the present invention is directed to a MEMS device, andtechnique of fabricating or manufacturing a MEMS device having anchorsto secure the mechanical structures to the substrate. The anchors of thepresent invention are comprised of a material that is relativelyunaffected by the release processes of the mechanical structures. Inthis regard, the etch release process are selective or preferential tothe material(s) securing the mechanical structures in relation to thematerial comprising the anchors. Moreover, the anchors of the presentinvention are secured to the substrate in such a manner that removal ofthe insulation layer has little to no affect on the anchoring of themechanical structures to the substrate.

With reference to FIG. 1, in one exemplary embodiment, MEMS 10 includesmicromachined mechanical structure 12 that is disposed on substrate 14,for example, an undoped semiconductor-like material, a glass-likematerial, or an insulator-like material. The MEMS 10 may also includedata processing electronics 16 to process and analyze informationgenerated by, and/or control or monitor the operation of micromachinedmechanical structure 12. In addition, MEMS 10 may also include interfacecircuitry 18 to provide information from micromachined mechanicalstructure 12 and/or data processing electronics 16 to an external device(not illustrated), for example, a computer, indicator/display and/orsensor.

The data processing electronics 16 and/or interface circuitry 18 may beintegrated in or on substrate 14. In this regard, MEMS 10 may be amonolithic structure including mechanical structure 12, data processingelectronics 16 and interface circuitry 18. The data processingelectronics 16 and/or interface circuitry 18 may also reside on aseparate, discrete substrate that, after fabrication, is bonded to or onsubstrate 14.

With reference to FIG. 2, in one embodiment, micromachined mechanicalstructure 12 includes mechanical structures 20 a-c and 22 a-f disposedon, above and/or in substrate 14. In particular, mechanical structures20 a-c may be “fixed” electrodes of “fixed” mechanical member 24. Themechanical structures 22 a-c may be “moveable” electrodes of “moveable”mechanical member 26 a and mechanical structures 22 d-f may be“moveable” electrodes of “moveable” mechanical member 26 b.

The mechanical structures 20 a-c and 22 a-f may be comprised of, forexample, materials in column IV of the periodic table, for examplesilicon, germanium, carbon; also combinations of these, for examplesilicon germanium, or silicon carbide; also of III-V compounds forexample gallium phosphide, aluminum gallium phosphide, or other III-Vcombinations; also combinations of III, IV, V, or VI materials, forexample silicon nitride, silicon oxide, aluminum carbide, or aluminumoxide; also metallic silicides, germanides, and carbides, for examplenickel silicide, cobalt silicide, tungsten carbide, or platinumgermanium silicide; also doped variations including phosphorus, arsenic,antimony, boron, or aluminum doped silicon or germanium, carbon, orcombinations like silicon germanium; also these materials with variouscrystal structures, including single crystalline, polycrystalline,nanocrystalline, or amorphous; also with combinations of crystalstructures, for instance with regions of single crystalline andpolycrystalline structure (whether doped or undoped).

Notably, mechanical structures 20 a-c and 22 a-f may be a portion of anaccelerometer, gyroscope or other transducer (for example, pressuresensor, strain sensor, tactile sensor, magnetic sensor and/ortemperature sensor), filter or resonator. The micromachined mechanicalstructure 12 may also include mechanical structures of a plurality oftransducers or sensors including one or more accelerometers, gyroscopes,pressure sensors, tactile sensors and temperature sensors. Wheremicromachined mechanical structure 12 is an accelerometer, mechanicalstructures 20 a-c and 22 a-f may be a portion of the interdigitated orcomb-like finger electrode arrays that comprise the sensing features ofthe accelerometer (see, for example, U.S. Pat. No. 6,122,964).

With continued reference to FIG. 2, micromachined mechanical structure12 may also include a contact area 28 disposed on or in substrate 14.The contact area 28 may provide an electrical path between micromachinedmechanical structure 12 and data processing electronics 16, interfacecircuitry 18 and/or an external device (not illustrated). The contactarea 24 may be comprised of, for example, silicon, (whether doped orundoped), germanium, silicon/germanium, silicon carbide, and galliumarsenide, and combinations and/or permutations thereof.

FIG. 3 illustrates a cross-sectional view of micromachined mechanicalstructure 12, including mechanical structures 20 a-c and 22 a-f, alongdotted line a-a′, in accordance with one embodiment of the presentinvention. The mechanical structures 20 a-c are affixed to substrate 14via anchors 30 a-c, respectively. In one embodiment, each mechanicalstructure 20 a-c is comprised of first crystalline portion 32 a-c (forexample, a polycrystalline portion) 32 a-c, respectively, and secondcrystalline portion (for example, monocrystalline portion) 34 a-c,respectively.

The anchors 30 a-c may be comprised of, for example, one or morematerial(s) that are relatively unaffected by the process(es) forreleasing the mechanical structures. In this regard, the etch releaseprocess(es) are selective and, as such, the material comprising anchors30 a-c are not substantially etched (or etched at all) relative to thematerial securing or surrounding mechanical structures 20 a-c and 22a-f.

The anchors 30 a-c are disposed on, or secured to, substrate 14 in sucha manner that removal of the insulation layer of the SOI substrate haslittle to no affect on the anchoring of mechanical structures 20 a-c and22 a-f to substrate 14.

In one embodiment, anchors 30 a-c may be silicon, silicon nitride,silicon carbide, and/or germanium, silicon/germanium, and galliumarsenide (and combinations thereof. Indeed, in those instances where theinsulation material of the SOI substrate is other than the commonsilicon oxide (for example, the sacrificial layer of the SOI substrateis a silicon nitride), anchors 30 a-c may be silicon oxide provided thatsilicon oxide is relatively unaffected by the process(es) of releasingthe mechanical structures.

The anchors 30 a-c may be deposited, formed and/or grown using, forexample, a low pressure (“LP”) chemically vapor deposited (“CVD”)process (in a tube or EPI reactor), plasma enhanced (“PE”) CVD process,or an atmospheric pressure (“AP”) CVD process. Indeed, all depositiontechniques, for depositing anchors 30 a-c, whether now known or laterdeveloped, are intended to be within the scope of the present invention.

With continued reference to FIG. 3, in one embodiment, mechanicalstructures 20 a-c are comprised of polycrystalline portion 32 a-c andmonocrystalline portion 34 a-c. The materials and/or surfaces, as wellas the techniques employed to deposit, form and/or grow mechanicalstructures 20 a-c, may determine the crystalline structure of theunderlying material. For example, in an epitaxial environment having apredetermined set of parameters, the monocrystalline portion ofmechanical structures 20 a-c will deposit, form and/or grow in an“advancing” manner and, as such polycrystalline portion 32 a-c willdeposit, form and/or grow in a “retreating” manner. In contrast, withanother predetermined set of parameters, monocrystalline portion 34 a-cof mechanical structures 20 a-c will deposit, form and/or grow in a“retreating” manner and, as such, polycrystalline portion 32 a-c willdeposit, from and/or grow in an “advancing” manner (see, FIG. 5). Thestructures and portions thereof may be deposited, formed and/or grown inthese or other manners and, as such, all deposition techniques for andcrystalline structures of mechanical structures 20 a-c, whether nowknown or later developed, are intended to be within the scope of thepresent invention.

With reference to FIG. 4A, the MEMS 10 is formed in or on SOI substrate36. The SOI substrate 36 includes first substrate layer 38 (for example,a semiconductor (such as silicon), glass or sapphire), insulation layer40 and first semiconductor layer 42. In one embodiment, SOI substrate 36is a SIMOX wafer. Where SOI substrate 36 is a SIMOX wafer such wafer maybe fabricated using well-known techniques including those disclosed,mentioned or referenced in U.S. Pat. Nos. 5,053,627; 5,080,730;5,196,355; 5,288,650; 6,248,642; 6,417,078; 6,423,975; and 6,433,342 andU.S. Published Patent Applications 2002/0081824 and 2002/0123211, thecontents of which are hereby incorporated by reference.

In another embodiment, SOI substrate 36 may be a conventional SOI waferhaving a relatively thin first semiconductor layer 42. In this regard,SOI substrate 36 having a relatively thin first semiconductor layer 42may be fabricated using a bulk silicon wafer which is implanted andoxidized by oxygen to thereby form a relatively thin SiO₂ underneath thesingle or mono crystalline wafer surface. In this embodiment, firstsemiconductor layer 42 (i.e., monocrystalline silicon) is disposed oninsulation layer 40 (i.e. silicon dioxide), having a thickness ofapproximately 350 nm, which is disposed on a first substrate layer 38(i.e., monocrystalline silicon), having a thickness of approximately 190nm.

Notably, all techniques for providing or fabricating SOI substrate 36,whether now known or later developed, are intended to be within thescope of the present invention.

With reference to FIGS. 4B and 4C, an exemplary method of fabricating ormanufacturing a micromachined mechanical structure 12 according to thepresent invention may begin with forming anchor openings 44 a-c andcontact opening 46 in insulation layer 40 and first semiconductor layer42 using well-known lithographic and etching techniques. In this way,selected portions of first semiconductor layer 40 are exposed tofacilitate contact thereto. Thereafter, anchors 30 a-c are formed inanchor openings 44 a-c using well-known deposition and lithographictechniques. As mentioned above, anchors 30 a-c may be comprised of, forexample, one or more material(s) that relatively unaffected by theprocess of releasing the mechanical structures. In this regard, thematerial is selective relative to the etch release process. Accordingly,anchors 30 a-c are disposed on, or secured to, substrate 14 in such amanner that removal of portions of insulation layer 40 near anchors 30a-c (during releases processes of mechanical structures 20 a-c and 22a-f).

With reference to FIG. 4D, active layer 48 may be deposited, formedand/or grown on anchors 30 a-c, insulation layer 40 and any exposedportion(s) of first substrate layer 38 (see, for example, contactopening 46 in FIG. 4C). The mechanical structures 20 a-c and 22 a-f areformed from active layer 48. The active layer 48 may be deposited,formed and/or grown using well-known techniques and from those materials(for example, semiconductors such as silicon, germanium,silicon-germanium or gallium-arsenide) described above with respect tomechanical structures 20 a-c and 22 a-f. In this embodiment, themonocrystalline portion 34 of active layer 48 is formed and/or grown inan “advancing” manner and, as such polycrystalline portion 32 a-c isformed and/or grown in a “retreating” manner.

Thereafter, with reference to FIG. 4E, mechanical structures 20 a-c and22 a-f, and contact area 28 may be formed using well-known lithographicand etching techniques. In this regard, trenches 50 a-g are formed inactive layer 48. In one embodiment, insulation layer 40 acts orfunctions as an etch stop during the formation of trenches 50 a-g.Notably, all techniques for forming or fabricating trenches 50 a-g,whether now known or later developed, are intended to be within thescope of the present invention.

The trenches 50 a-g, in addition to defining the features of mechanicalstructures 20 a-c and 22 a-f, may also permit etching and/or removal ofat least selected portions of insulation layer 40. With reference toFIG. 4F, using well-known etching techniques and materials, insulationlayer 40 is etched or removed to release mechanical structures 20 a-cand 22 a-f. For example, in one embodiment, where insulation layer 40 iscomprised of silicon dioxide, selected portions may be removed/etchedusing well-known wet etching techniques and buffered HF mixtures (i.e.,a buffered oxide etch) or well-known vapor etching techniques usingvapor HF. Proper design of mechanical structures 20 a-d and control ofthe HF etching process parameters may permit insulation layer 40 to besufficiently removed or etched to release mechanical structures 20 a-cand 22 a-f and permit proper operation of MEMS 10.

In another embodiment, where insulation layer 40 is comprised of siliconnitride, selected portions may be removed/etched using phosphoric acid.Again, proper design of mechanical structures 20 a-c and 22 a-f, andcontrol of the wet etching process parameters, may permit insulationlayer 40 to be sufficiently etched which will release mechanicalstructures 20 a-c and 22 a-f.

It should be noted that there are: (1) many suitable materials forinsulation layer 40 (for example, silicon dioxide, silicon nitride, anddoped and undoped glass-like materials, e.g., phosphosilicate (“PSG”) orborophosphosilicate (“BPSG”)) and spin on glass (“SOG”)), (2) manysuitable/associated etchants (for example, a buffered oxide etch,phosphoric acid, and alkali hydroxides such as, for example, NaOH andKOH), and (3) many suitable etching or removal techniques (for example,wet, plasma, vapor or dry etching), to eliminate, remove and/or etchinsulation layer 40. Accordingly, all materials, etchants and etchtechniques, and permutations thereof, for eliminating, removing and/oretching, whether now known or later developed, are intended to be withinthe scope of the present invention.

As mentioned above, anchors 30 a-c remain relatively unaffected by theremoval of insulation layer 40. In this regard, the etch or removalprocess is selective to insulation layer 40. In those instances whereanchors 30 a-c are etched during the removal or etching of insulationlayer 40, it may be advantageous to select materials that provide asignificant etch selectively ratio (for example, greater than 10:1, 25:1or 50:1, and preferably greater than 100:1) and/or to appropriately timethe etch so that anchors 30 a-c are not substantially affected. In thisway, anchors 30 a-c may provide the anchoring requirements of mechanicalstructures 20 a-c.

The MEMS 10 may be sealed in chamber 52 using conventional encapsulationtechniques and structures. With continued reference to FIG. 4F, in oneembodiment, MEMS 10 is encapsulated using, for example, cap 52 (asemiconductor or glass-like substrate) that is bonded to substrate 14.Other packaging techniques are also suitable (for example, a TO-8“can”). Indeed, all encapsulation techniques, whether now known or laterdeveloped, are intended to be within the scope of the present invention.

For example, the encapsulation techniques described and illustrated innon-provisional patent application entitled “MicroelectromechanicalSystems, and Method of Encapsulating and Fabricating Same”, which wasfiled on Jun. 4, 2003 and assigned Ser. No. 10/454,867 (hereinafter“Microelectromechanical Systems and Method of Encapsulating PatentApplication”), may be employed in conjunction with the anchors andanchoring techniques described and illustrated herein. For the sake ofbrevity, the inventions described and illustrated in theMicroelectromechanical Systems and Method of Encapsulating PatentApplication, implemented in conjunction with the inventions describedand illustrated herein, will not be repeated but will only besummarized. It is expressly noted, however, that the entire contents ofthe Microelectromechanical Systems and Method of Encapsulating PatentApplication, including for example, the features, attributes,alternatives, materials, techniques and advantages of all of theinventions, are incorporated by reference herein.

Briefly, with reference to FIG. 6, micromachined mechanical structure 12includes mechanical structures 20 a-c, anchored in the manner asdescribed above, mechanical structures 22 a-f, and contact area 28. Inaddition, first and second encapsulation layers 56 and 58, respectively,may seal chamber 60 using any of the techniques, materials orembodiments described in the Microelectromechanical Systems and Methodof Encapsulating Patent Application. Further, contact via 62 provideselectrical access to contact 28.

In particular, with reference to FIGS. 7A and 7B, an exemplary method offabricating or manufacturing a micromachined mechanical structure 12using the encapsulation techniques of Microelectromechanical Systems andMethod of Encapsulating Patent Application may begin with a partiallyformed device including mechanical structures 20 a-c, anchored in themanner as described above, mechanical structures 22 a-f, and contactarea 28 (see, FIG. 7A). Thereafter, sacrificial layer 64 may bedeposited and patterned to expose a portion of the contact area 28 tofacilitate electrical connection thereto (see, FIG. 7B).

With reference to FIG. 7C, after deposition of sacrificial layer 64,first encapsulation layer 56 may be deposited, formed and/or grown. Thefirst encapsulation layer 56 may be, for example, a silicon-basedmaterial (for example, silicon/germanium, silicon carbide,monocrystalline silicon, polycrystalline silicon or amorphous silicon,whether doped or undoped), germanium, and gallium arsenide (andcombinations thereof), which is deposited and/or formed using, forexample, an epitaxial, a sputtering or a CVD-based reactor (for example,APCVD, LPCVD, or PECVD). The deposition, formation and/or growth may beby a conformal process or non-conformal process.

With reference to FIGS. 7D and 7E, first encapsulation layer 56 may beetched (see, FIG. 7D) to form vents 66 that are intended to permitetching and/or removal of at least selected portions of insulation layer40 and sacrificial layer 64 (see, FIG. 7D). Again, proper design ofmechanical structures 20 a-c and 22 a-f, insulation layer 40 andsacrificial layer 64, and control of the etch process parameters maypermit the insulation layer 40 and sacrificial layer 64 to besufficiently etched to release mechanical structures 20 a-c and 22 a-fand permit proper operation of MEMS 10 (see, FIG. 7E).

After releasing mechanical elements 20 a-c and 22 a-f, secondencapsulation layer 58 may be deposited, formed and/or grown (see, FIG.7F). The second encapsulation layer 58 may be, for example, asilicon-based material (for example, a monocrystalline silicon,polycrystalline silicon, silicon-germanium, and/or combinationsthereof), which is deposited using, for example, an epitaxial, asputtering or a CVD-based reactor (for example, APCVD, LPCVD, or PECVD).The deposition, formation and/or growth may be by a conformal process ornon-conformal process. The material may be the same as or different fromfirst encapsulation layer 56. It may be advantageous, however, to employthe same material to form first and second encapsulation layers 56 and58 in order to enhance the “seal” of chamber 60.

As discussed in detail in Microelectromechanical Systems and Method ofEncapsulating Patent Application, in certain embodiments, secondencapsulation layer 58 may be doped with impurities having an oppositeconductivity relative to the impurities in first encapsulation layer 56.In this way, upon completion of the sealing or encapsulation process,junctions surrounding contact via 62 are formed which electrically“isolate” contact via 62 (and contact area 28) from, for example, nearbyelectrically conductive regions such as field regions.

In addition, in another set of embodiments, it may be advantageous tosubstantially planarized the exposed surface of second encapsulationlayer 58 using, for example, polishing techniques (for example, CMP).The planarization process removes a portion of second encapsulationlayer 58 to provide a “smooth” surface layer and/or (substantially)planar surface. Indeed, the planarization process may remove asufficient portion of second encapsulation layer 58 so that contact via60 is electrically isolated by a ring of oppositely doped semiconductorlayer 58 (see, FIG. 7G). This exposed planar surface may further providea well-prepared base upon which integrated circuits (for example, CMOStransistors) and/or micromachined mechanical structure 12 may befabricated on or in using well-known fabrication techniques andequipment.

In another set of embodiments, contact via 62 is electrically “isolated”using a trench technique. For example, the encapsulation and isolationtechniques described and illustrated in non-provisional patentapplication entitled “Microelectromechanical Systems Having TrenchIsolated Contacts, and Methods of Fabricating Same”, which was filed onJun. 4, 2003 and assigned Ser. No. 10/455,555 (hereinafter“Microelectromechanical Systems Having Trench Isolated Contacts PatentApplication”), may be employed in conjunction with the anchors andanchoring techniques described and illustrated herein. For the sake ofbrevity, the inventions described and illustrated in theMicroelectromechanical Systems Having Trench Isolated Contacts PatentApplication, implemented in conjunction with the inventions describedand illustrated herein, will not be repeated but will only besummarized. It is expressly noted, however, that the entire contents ofthe Microelectromechanical Systems Having Trench Isolated ContactsPatent Application, including for example, the features, attributes,alternatives, materials, techniques and advantages of all of theinventions, are incorporated by reference herein.

Briefly, with reference to FIG. 8, micromachined mechanical structure 12includes mechanical structures 20 a-c, anchored in the manner asdescribed above, mechanical structures 22 a-f, and contact area 28. Thefirst and second encapsulation layers 56 and 58, respectively, may sealchamber 60 using any of the techniques, materials or embodimentsdescribed in the Microelectromechanical Systems and Method ofEncapsulating Patent Application and/or Microelectromechanical SystemsHaving Trench Isolated Contacts Patent Application. In addition,micromachined mechanical structure 12 includes dielectric isolationregions 68 a and 68 b that electrically isolate contact area 28 (andcontact via 62) from surrounding or nearby electrically conductiveregions.

In particular, with reference to FIGS. 9A, 9B and 9C, an exemplarymethod of fabricating or manufacturing a micromachined mechanicalstructure 12 using the encapsulation and isolation techniques ofMicroelectromechanical Systems Having Trench Isolated Contacts PatentApplication may begin with a partially formed device includingmechanical structures 20 a-c, anchored in the manner as described above,mechanical structures 22 a-f, and contact area 28. The micromachinedmechanical structure 12 has been released and sealed using, for example,techniques that are substantially similar to that described above (see,FIG. 9A). Thereafter, trenches 70 a and 70 b may be etched (see, FIG.9B) and insulating material 74 may be deposited in trenches 70 a and 70b to form dielectric isolation regions 68 a and 68 b, respectively (see,FIG. 9C).

It may be advantageous to partially etch or remove sacrificial layer 64such that contact 28 and/or contact via 62 remain partially,substantially or entirely surrounded by portions of sacrificial layer64. For example, with reference to FIGS. 9A and 9B, while mechanicalstructures 20 a-c and 22 a-f are released, a portion 72 of sacrificiallayer 64 (i.e., juxtaposed electrical contact area 28 may remain afteretching or removing sacrificial layer 64. This portion of sacrificiallayer 64 may function as an etch stop during formation of trenches 70 aand 70 b. Under this circumstance, it may be advantageous to employmaterial(s) for sacrificial layer 64 that is consistent with the processto form trenches 70 a and 70 b such that the remaining portions of thesecond sacrificial layer 64 may function as an etch stop duringformation of trenches 70 a and 70 b. This notwithstanding, sacrificiallayer 64 may be, for example, silicon dioxide, silicon nitride, anddoped and undoped glass-like materials, and SOG.

It should be noted that, in another embodiment, an insignificant amountof material comprising sacrificial layer 64 (or little to no sacrificiallayer 64) remains after etching sacrificial layer 64. As such, materialsfor sacrificial layer 64 may be selected with little regard tosubsequent processing. Moreover, in this case, the etch of trenches 70 aand 70 b may be, for example, timed so that dielectric isolation regions68 a and 68 b provide appropriate electrical isolation.

The insulating material 74 may be, for example, silicon dioxide, siliconnitride, BPSG, PSG, or SOG, or combinations thereof. It may beadvantageous to employ silicon nitride because silicon nitride may bedeposited more a more conformal manner than silicon oxide. Moreover,silicon nitride is compatible with CMOS processing, in the event thatMEMS 10 includes CMOS integrated circuits.

With reference to FIGS. 10A-D, dielectric isolation regions 68 a and 68b may also include a slight taper in order to facilitate the formationof isolation regions 68 a and 68 b (see, FIG. 10A). In addition,dielectric isolation regions 68 a and 68 b may include a plurality ofmaterials, including, for example, a first material 68 aa (for example,silicon dioxide, silicon nitride, BPSG, PSG, or SOG) and a secondmaterial 68 ab (for example, a silicon based material such aspolycrystalline silicon). In this way, an electrical isolation isprovided by way of insulating material 68 aa while a limited amount ofdielectric is exposed to the surface of micromachined mechanicalstructure 12 (see, FIGS. 10A-D).

Notably, after formation of dielectric isolation regions 68 a and 68 b,it may be advantageous to substantially planarize micromachinedmechanical structure 12 to provide a “smooth” surface layer and/or(substantially) planar surface. In this way, the exposed planar surfaceof micromachined mechanical structure 12 may be well-prepared base uponwhich integrated circuits (for example, CMOS transistors) and/ormicromachined mechanical structure 12 may be fabricated on or in usingwell-known fabrication techniques and equipment.

In another embodiment, portions 72 a and 72 b of sacrificial layer 64are defined prior to releasing mechanical structures 20 a-c and 22 a-fby way of etching or removing sacrificial layer 64. With reference toFIGS. 11A-D, additional openings 80 a and 80 b are formed or patternedin sacrificial layer 64 (see, FIG. 11A) to provide regions to depositand form etch stop portions 82 a and 82 b (see, FIG. 11B). The etch stopportions 82 a and 82 b may be the same material as anchors 30 a-c. Inthis way, portions 72 a and 72 b of sacrificial layer 64 remainrelatively intact during the processes that release of mechanicalstructures 20 a-c and 22 a-f. After mechanical structures 20 a-c and 22a-f have been released and first and second encapsulation layers 56 and58 have been deposited, formed and/or grown (see, FIG. 11C), trenches 70a and 70 b are formed or etched and thereafter filled, as describedabove, to provide dielectric isolation regions 68 a and 68 b (see, FIG.11D).

Notably, the techniques of fabricating dielectric isolation regions 68 aand 68 b, as illustrated in FIGS. 11A-D (and FIGS. 11E and 11F), may beimplemented in MEMS 10 that does not include anchors 30 a-c. Indeed, theembodiment of FIGS. 11A-D (and FIGS. 11E and 11F) may be implementedusing any anchoring technique or structure including any of theembodiments described and illustrated in Microelectromechanical SystemsHaving Trench Isolated Contacts Patent Application. For the sake ofbrevity, those embodiments, and combinations thereof, will not berepeated but are incorporated by reference herein.

In another embodiment, dielectric isolation regions 68 a and 68 b may beformed or completed while processing the “back-end” of the integratedcircuit fabrication of MEMS 10. In this regard, with reference to FIGS.9C, 9D, 11E and 11F, during deposition, formation and/or growth ofinsulation layer 74, trenches 70 a and 70 b may also be etched andfilled to form dielectric isolation regions 68 a and 68 b. Thereafter,contact opening 76 may be etched to facilitate electrical connection tocontact area 28, via contact plug 62 (see, FIG. 9C and FIG. 11E). Aconductive layer 78 may then be deposited to provide the appropriateelectrical connection to contact 28 (see, FIG. 9D and FIG. 11F).

Notably, in the embodiments of FIGS. 9C and 9D, and 11E and 11F, theprocessing pertaining to the dielectric isolation regions 68 a and 68 bmay be “combined” with the insulating and contact formation step of the“back-end” of the integrated circuit fabrication of MEMS 10. In thisway, fabrication costs may be reduced.

Thus, in one set of embodiments, a monolithic structure may includemechanical structure 12 and data processing electronics 16 and/orinterface circuitry 18 that are integrated on or in a common substrate.With reference to FIGS. 12A-12E, MEMS 10 includes micromachinedmechanical structure 12, having structures 20 a-20 c and 22 a-c andcontact area 28, as well as data processing electronics 16, includingintegrated circuits 84 disposed in a field region or other semiconductorregion having a single crystalline structure. The integrated circuits 54may be fabricated using conventional techniques before trenches 50 a-gare formed (see, for example, FIG. 4E). As mentioned above, mechanicalstructures 20 a-20 c and 22 a-c (and contact 24) may be formed primarilyfrom, for example, a single crystalline material (FIGS. 12A, 12C, 12Dand 12E) or a polycrystalline material (FIG. 12B).

With reference to FIG. 13A, contact 28 may be accessed directly byintegrated circuitry 84 via conductive layer 78. In particular, in oneembodiment, an insulation material may be deposited in trench 86 betweenthe field region on which integrated circuitry 84 is formed and contact28. Thereafter, a low resistance electrical path, for example,conductive layer 78, may be deposited and patterned to facilitateconnection.

It should be noted that integrated circuits 54 may be fabricated usingconventional techniques after definition of mechanical structure 12using, for example, the techniques described and illustrated inMicroelectromechanical Systems and Method of Encapsulating PatentApplication and/or Microelectromechanical Systems Having Trench IsolatedContacts Patent Application (see, for example, FIG. 13B). In thisregard, after fabrication and encapsulation of mechanical structure 12,having anchors 30 a-c, integrated circuits 84 may be fabricated usingconventional techniques and interconnected to contact area 28 by way ofconductive layer 78. In particular, as illustrated and described inMicroelectromechanical Systems and Method of Encapsulating PatentApplication (for example, FIGS. 12A-C thereof) and/orMicroelectromechanical Systems Having Trench Isolated Contacts PatentApplication (for example, FIGS. 14A-E thereof, the contact area isaccessed directly by integrated circuitry 84 via a low resistanceelectrical path (i.e., conductive layer 78) that facilitates a goodelectrical connection. The insulation layer 74 may be deposited, formedand/or grown and patterned and, thereafter, conductive layer 78 (forexample, a heavily doped polysilicon or metal such as aluminum,chromium, gold, silver, molybdenum, platinum, palladium, tungsten,titanium, and/or copper) is formed. Notably, as mentioned above, all ofthe embodiments described and illustrated in MicroelectromechanicalSystems and Method of Encapsulating Patent Application and/orMicroelectromechanical Systems Having Trench Isolated Contacts PatentApplication may be fabricated using the substrate anchoring techniquesdescribed and illustrated in this application. For the sake of brevity,those combinations will not be repeated but are incorporated byreference herein.

There are many inventions described and illustrated herein. Whilecertain embodiments, features, materials, configurations, attributes andadvantages of the inventions have been described and illustrated, itshould be understood that many other, as well as different and/orsimilar embodiments, features, materials, configurations, attributes,structures and advantages of the present inventions that are apparentfrom the description, illustration and claims. As such, the embodiments,features, materials, configurations, attributes, structures andadvantages of the inventions described and illustrated herein are notexhaustive and it should be understood that such other, similar, as wellas different, embodiments, features, materials, configurations,attributes, structures and advantages of the present inventions arewithin the scope of the present invention.

For example, with reference to FIG. 5, mechanical structures 20 a-c maybe comprised of substantially polycrystalline structures. As mentionedabove, active layer 48 may be deposited, formed and/or grown using apredetermined set of parameters that deposit, form and/or growmonocrystalline portion 34 a-c of mechanical structures 20 a-c in a“retreating” manner. As such, polycrystalline portion 32 a-c willdeposit, from and/or grow in an “advancing” manner. Thus, in thisembodiment, mechanical structures 20 a-c are substantiallypolycrystalline, for example, polycrystalline silicon.

The environment (for example, the gas or gas vapor pressure) withinchambers 52 and 60 determine to some extent the mechanical damping formechanical structures 20 a-c and 22 a-f. In this regard, chambers 52 and60 may include a fluid that is “trapped”, “sealed” and/or containedwithin chambers 52 and 60. The state of the fluid within chambers 52 and60 (for example, the pressure) may be determined using conventionaltechniques and/or using those techniques described and illustrated innon-provisional patent application entitled “Electromechanical Systemhaving a Controlled Atmosphere, and Method of Fabricating Same”, whichwas filed on Mar. 20, 2003 and assigned Ser. No. 10/392,528 (hereinafter“the Electromechanical System having a Controlled Atmosphere PatentApplication”). For the sake of brevity, all of the inventions describedand illustrated in the Electromechanical System having a ControlledAtmosphere Patent Application will not be repeated here. It is expresslynoted, however, that the entire contents of the Electromechanical Systemhaving a Controlled Atmosphere Patent Application, including forexample, the features, attributes, alternatives, materials, techniquesand advantages of all of the inventions, are incorporated by referenceherein.

Further, as mentioned above, the anchors and anchoring techniquesdescribed herein may be implemented in conjunction with mechanicalstructures 12 having one or more transducers or sensors which maythemselves include multiple layers that are vertically and/or laterallystacked or interconnected as illustrated in MicroelectromechanicalSystems and Method of Encapsulating Patent Application (see, forexample, micromachined mechanical structure 12 b of FIG. 11A; mechanicalstructure 12 of FIGS. 11B and 11C; and mechanical structures 20 a and 20b, contact areas 24 a and 24 b, and buried contacts 24′ and 24″ of FIG.11D) and/or Microelectromechanical Systems Having Trench IsolatedContacts Patent Application (see, for example, micromachined mechanicalstructure 12 b of FIG. 13A; micromachined mechanical structure 12 ofFIGS. 13B and 13C; and mechanical structures 20 a and 20 b, contactareas 24 a and 24 b, and buried contacts 24′ and 24″ of FIG. 13D).Accordingly, any and all of the anchoring embodiments illustrated anddescribed herein may be implemented in the embodiments ofMicroelectromechanical Systems and Method of Encapsulating PatentApplication and/or Microelectromechanical Systems Having Trench IsolatedContacts Patent Application that include multiple layers of mechanicalstructures, contacts areas and buried contacts that are verticallyand/or laterally stacked or interconnected (see, for example,micromachined mechanical structure 12 of FIGS. 11B, 11C and 11D ofMicroelectromechanical Systems and Method of Encapsulating PatentApplication and/or micromachined mechanical structure 12 of FIGS. 13B,13C and 13D of Microelectromechanical Systems Having Trench IsolatedContacts Patent Application). Under this circumstance, the mechanicalstructures may be fabricated using anchoring techniques described inthis application wherein the mechanical structures include one or moreprocessing steps to provide the vertically and/or laterally stackedand/or interconnected multiple layers (see, for example, fixed electrode20 a of FIG. 14A).

Moreover, the anchors and anchoring techniques described herein may beimplemented to secure, anchor and/or affix any of the contacts to astructure or substrate (for example, substrate 38). Thus, any or all ofthe contacts, regardless of level (for example, contact 24 of FIG. 14B)may be fixed or secured using the anchors and anchoring techniquesdescribed herein.

The term “depositing” and other forms (i.e., deposit, deposition anddeposited) in the claims, means, among other things, depositing,creating, forming and/or growing a layer of material using, for example,a reactor (for example, an epitaxial, a sputtering or a CVD-basedreactor (for example, APCVD, LPCVD, or PECVD)).

Further, in the claims, the term “contact” means a conductive region,partially or wholly disposed outside the chamber, for example, thecontact area and/or contact via.

Finally, it should be further noted that while the present inventionshave been described in the context of microelectromechanical systemsincluding micromechanical structures or elements, the present inventionsare not limited in this regard. Rather, the inventions described hereinare applicable to other electromechanical systems including, forexample, nanoelectromechanical systems. Thus, the present inventions arepertinent to electromechanical systems, for example, gyroscopes,resonators, temperatures sensors and/or accelerometers, made inaccordance with fabrication techniques, such as lithographic and otherprecision fabrication techniques, which reduce mechanical components toa scale that is generally comparable to microelectronics.

1. A microelectromechanical device comprising: a substrate; aninsulation layer disposed on the substrate; a first semiconductor layerdisposed on or above the insulation layer; an anchor that is disposed inan opening in the insulation layer and the first semiconductor layer andcontacts the substrate, wherein the anchor includes a material that isdifferent from the insulation layer; a second semiconductor layerdisposed on the anchor; a fixed electrode, formed, in part, from thefirst and second semiconductor layers, wherein the fixed electrode isaffixed to the substrate via the anchor; a moveable electrode, formed,in part, from the second semiconductor layer, wherein the moveableelectrode is disposed, at least in part, in a chamber; a firstencapsulation layer disposed over the moveable electrode, wherein thefirst encapsulation layer is at least a portion of a wall of thechamber; and a second encapsulation layer, deposited on the firstencapsulation layer, to seal the chamber.
 2. The device of claim 1wherein the insulation layer includes silicon nitride or silicon oxide.3. The device of claim 1 wherein the insulation layer includes siliconoxide and the anchor material includes silicon nitride, silicon carbide,germanium, silicon/germanium or gallium arsenide.
 4. The device of claim1 wherein the insulation layer includes silicon nitride and the anchormaterial includes silicon, silicon oxide, silicon carbide, germanium,silicon/germanium or gallium arsenide.
 5. The device of claim 1 whereina substantial portion of the fixed electrode overlying the anchormaterial includes a monocrystalline silicon.
 6. The device of claim 1wherein a substantial portion of the fixed electrode overlying theanchor material includes a polycrystalline silicon.
 7. The device ofclaim 1 further including a third encapsulation layer disposed on thesecond encapsulation layer.
 8. The device of claim 7 wherein the thirdencapsulation layer is a metal material including aluminum, chromium,gold, silver, molybdenum, platinum, palladium, tungsten, titanium,silicide and/or copper.
 9. The device of claim 7 wherein the thirdencapsulation layer is an insulating material including silicon oxide,silicon nitride, BPSG, PSG and/or SOG.
 10. A microelectromechanicaldevice comprising: a substrate; an insulation layer disposed on thesubstrate; a first semiconductor layer disposed on or above theinsulation layer; an anchor that is disposed in an opening in theinsulation layer and the first semiconductor layer and contacts thesubstrate, wherein the anchor includes a material that is different fromthe insulation layer; a second semiconductor layer disposed on theanchor and on the first semiconductor layer; a fixed electrode, formed,in part, from the first and second semiconductor layers, wherein thefixed electrode is affixed to the substrate via the anchor; a moveableelectrode, formed, in part, from the second semiconductor layer, whereinthe moveable electrode is disposed, at least in part, in a chamber; afirst encapsulation layer, disposed over at a portion of the moveableelectrode, wherein the first encapsulation layer is at least a portionof a wall of the chamber; and a second encapsulation layer, deposited onthe first encapsulation layer, to seal the chamber, wherein the secondencapsulation layer includes a semiconductor material.
 11. The device ofclaim 10 wherein the first encapsulation layer includes a poroussemiconductor material.
 12. The device of claim 10 wherein the secondencapsulation layer includes polycrystalline silicon, silicon carbide,silicon/germanium, germanium, or gallium arsenide.
 13. The device ofclaim 10 wherein the insulation layer includes silicon oxide and theanchor material includes silicon nitride, silicon carbide, germanium,silicon/germanium or gallium arsenide.
 14. The device of claim 10wherein the insulation layer includes silicon nitride and the anchormaterial includes silicon, silicon oxide, silicon carbide, germanium,silicon/germanium or gallium arsenide.
 15. The device of claim 10wherein the second encapsulation layer includes an epitaxially depositedpolycrystalline silicon.
 16. The device of claim 10 further including athird encapsulation layer disposed on the second encapsulation layer tofurther seal the chamber.
 17. The device of claim 16 wherein the thirdencapsulation layer is a metal material including aluminum, chromium,gold, silver, molybdenum, platinum, palladium, tungsten, titanium,silicide and/or copper.
 18. The device of claim 16 wherein the thirdencapsulation layer is an insulating material including silicon oxide,silicon nitride, BPSG, PSG and/or SOG.
 19. The device of claim 10further including: a contact; and a trench, disposed around at least aportion of the contact, wherein the trench is disposed outside thechamber and wherein the trench includes an insulating material disposedtherein.
 20. The device of claim 19 wherein the trench surrounds aportion of the contact that is disposed outside of the chamber.
 21. Thedevice of claim 19 wherein the insulating material disposed in thetrench is silicon nitride or silicon oxide.
 22. A microelectromechanicaldevice comprising: a substrate; an insulation layer disposed on thesubstrate; a first semiconductor layer disposed on or above theinsulation layer; an anchor that is disposed in an opening in theinsulation layer and the first semiconductor layer and contacts thesubstrate, wherein the anchor includes a material that is different fromthe insulation layer; a second semiconductor layer, disposed on theanchor; a fixed electrode, formed, in part, from the secondsemiconductor layer, wherein the fixed electrode is affixed to thesubstrate via the anchor; a moveable electrode, formed, in part, fromthe second semiconductor layer, wherein the moveable electrode isdisposed, at least in part, in a chamber; a first encapsulation layer,disposed over at least a portion of the moveable electrode, wherein thefirst encapsulation layer is at least a portion of a wall of thechamber; and a second encapsulation layer, deposited on the firstencapsulation layer, to seal the chamber, wherein the secondencapsulation layer includes a semiconductor material.
 23. The device ofclaim 22 wherein the first encapsulation layer includes a poroussemiconductor material.
 24. The device of claim 23 wherein the secondencapsulation layer includes polycrystalline silicon, silicon carbide,silicon/germanium, germanium, or gallium arsenide.
 25. The device ofclaim 22 wherein the insulation layer includes silicon oxide and theanchor material includes silicon nitride, silicon carbide, germanium,silicon/germanium or gallium arsenide.
 26. The device of claim 22wherein the insulation layer includes silicon nitride and the anchormaterial includes silicon, silicon oxide, silicon carbide, germanium,silicon/germanium or gallium arsenide.
 27. The device of claim 22wherein a substantial portion of the fixed electrode overlying theanchor material is a monocrystalline silicon or a polycrystallinesilicon.
 28. The device of claim 22 wherein the second encapsulationlayer is an epitaxially deposited polycrystalline silicon.
 29. Thedevice of claim 22 further including a third encapsulation layerdisposed on the second encapsulation layer.
 30. The device of claim 29wherein the third encapsulation layer is a metal material includingaluminum, chromium, gold, silver, molybdenum, platinum, palladium,tungsten, titanium, silicide and/or copper.
 31. The device of claim 29wherein the third encapsulation layer is an insulating materialincluding silicon oxide, silicon nitride, BPSG, PSG and/or SOG.
 32. Thedevice of claim 22 further including: a contact; and a trench, disposedaround at least a portion of the contact, wherein the trench is disposedoutside the chamber and wherein the trench includes an insulatingmaterial disposed therein.
 33. The device of claim 32 wherein the trenchsurrounds a portion of the contact that is disposed outside of thechamber.
 34. The device of claim 32 wherein the insulating materialdisposed in the trench is silicon nitride or silicon oxide.